the speed of camera rotations when using the numbers of the numpad?
Yes, go to User Preferences/Interface, and here play with the Smooth View and Rotation Angle settings.


  Smooth View
      Length of time the animation takes when changing the view with the numpad. Reduce to zero to remove the animation.
  
  Rotation Angle
      Rotation step size in degrees, when Numpad4, Numpad6, Numpad8, or Numpad2 are used to rotate the 3D View.